Java深度复制和浅度复制

关键字: java 潜拷贝和深拷贝 .java里的clone分为： 

A:浅复制（浅克隆）:浅复制仅仅复制所考虑的对象，而不复制它所引用的对象。 

b:深复制（深克隆）：深复制把要复制的对象所引用的对象都复制了一遍。 

Java中对象的克隆,为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。必须要遵循下面三点 

1.在派生类中覆盖基类的clone()方法，并声明为public【Object类中的clone()方法为protected的】。 

2.在派生类的clone()方法中，调用super.clone()。 

3.在派生类中实现Cloneable接口。 

 

Object类里的clone方法是浅复制（浅克隆） 

 

浅复制（浅克隆）的例子如下：

package com.test;

//浅复制（浅克隆）:浅复制仅仅复制所考虑的对象，而不复制它所引用的对象。

//深复制（深克隆）：深复制把要复制的对象所引用的对象都复制了一遍。

//

//Java中对象的克隆,为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。必须要遵循下面三点

//1.在派生类中覆盖基类的clone()方法，并声明为public【Object类中的clone()方法为protected的】。

//2.在派生类的clone()方法中，调用super.clone()。

//3.在派生类中实现Cloneable接口。

//<SPANstyle="COLOR: red">Object类里的clone方法是浅复制（浅克隆）</SPAN>public class CloneTest {

 public staticvoid main(String[] args) throws Exception{

  //teacher对象将被clone出来的Student对象共享.

Teacher teacher = new Teacher();  teacher.setAge(40);  teacher.setName("Teacher zhang");    Student student1 = new Student();  student1.setAge(20);  student1.setName("zhangsan");  student1.setTeacher(teacher);    //复制出来一个对象student2  Student student2 = (Student)student1.clone();  System.out.println(student2.getAge());  System.out.println(student2.getName());      System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName());      //修改student2的引用对象  student2.getTeacher().setAge(50);  student2.getTeacher().setName("Teacher Li");    System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName()); }}class Teacher { public int age; public String name;  public int getAge() {  return age; } public void setAge(int age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } 

输出结果为：

20

zhangsan

~~~~~~~~~~~~~~~~~~~~~~

40

Teacher zhang

~~~~~~~~~~~~~~~~~~~~~~

50

Teacher Li

2.深复制（深Clone）例子：

package com.test1;//深clonepublic class DeepCloneTest { public static void main(String[] args) throws Exception{  //teacher对象将不被clone出来的Student对象共享.  Teacher teacher = new Teacher();  teacher.setAge(40);  teacher.setName("Teacher zhang");    Student student1 = new Student();  student1.setAge(20);  student1.setName("zhangsan");  student1.setTeacher(teacher);    //复制出来一个对象student2  Student student2 = (Student)student1.clone();  System.out.println(student2.getAge());  System.out.println(student2.getName());      System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName());      //修改student2的引用对象  student2.getTeacher().setAge(50);  student2.getTeacher().setName("Teacher Li");    System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName()); }}class Teacher implements Cloneable{ public int age; public String name;  public int getAge() {  return age; } public void setAge(int age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } @Override public Object clone() throws CloneNotSupportedException {  return super.clone(); } }class Student implements Cloneable{  public int age ; public String name; public Teacher teacher; public int getAge() {  return age; } public void setAge(int age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } public Teacher getTeacher() {  return teacher; } public void setTeacher(Teacher teacher) {  this.teacher = teacher; } @Override public Object clone() throws CloneNotSupportedException {  Student student = (Student)super.clone();  //将引用的对象teacher也clone下  student.setTeacher((Teacher)(student.getTeacher().clone()));  return student; }  }

输出结果为：

20

zhangsan

~~~~~~~~~~~~~~~~~~~~~~

40

Teacher zhang

~~~~~~~~~~~~~~~~~~~~~~

40

Teacher zhang

3.利用序列化来做深复制,把对象写到流里的过程是序列化（Serilization）过程，而把对象从流中读出来的过程则叫做反序列化（Deserialization）过程。应当指出的是，写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。，利用这个特性，可以做深拷贝

package com.test3;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.io.Serializable;//利用序列化来做深复制//深clonepublic class DeepCloneTest { public static void main(String[] args) throws Exception{  //teacher对象将不被clone出来的Student对象共享.  Teacher teacher = new Teacher();  teacher.setAge(40);  teacher.setName("Teacher zhang");    Student student1 = new Student();  student1.setAge(20);  student1.setName("zhangsan");  student1.setTeacher(teacher);    //复制出来一个对象student2  Student student2 = (Student)student1.deepCopy();  System.out.println(student2.getAge());  System.out.println(student2.getName());      System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName());      //修改student2的引用对象  student2.getTeacher().setAge(50);  student2.getTeacher().setName("Teacher Li");    System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  System.out.println(student1.getTeacher().getAge());  System.out.println(student1.getTeacher().getName()); }}class Teacher implements Serializable{  private static final long serialVersionUID = -8834559347461591191L;  public int age; public String name;  public int getAge() {  return age; } public void setAge(int age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } }class Student implements Serializable{  //serialVersionUID 如果你的对象序列化后存到硬盘上面后，可是后来你却更改了类的field(增加或减少或改名)，当你反序列化时，就会出现Exception的，这样就会造成不兼容性的问题。  //但当serialVersionUID相同时，它就会将不一样的field以type的缺省值赋值(如int型的是0,String型的是null等)，这个可以避开不兼容性的问题。所以最好给serialVersionUID赋值 private static final long serialVersionUID = 7991552226614088458L;  public int age ; public String name; public Teacher teacher; public int getAge() {  return age; } public void setAge(int age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } public Teacher getTeacher() {  return teacher; } public void setTeacher(Teacher teacher) {  this.teacher = teacher; }  public Object deepCopy() throws Exception{  //将该对象序列化成流,因为写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。所以利用这个特性可以实现对象的深拷贝  ByteArrayOutputStream bos = new ByteArrayOutputStream();  ObjectOutputStream oos = new ObjectOutputStream(bos);  oos.writeObject(this);  //将流序列化成对象  ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());  ObjectInputStream ois = new ObjectInputStream(bis);  return ois.readObject(); }  }

输出结果为：

20

zhangsan

~~~~~~~~~~~~~~~~~~~~~~

40

Teacher zhang

~~~~~~~~~~~~~~~~~~~~~~

40

Teacher zhang